US20110132896A1 - Heater plate with embedded hyper-conductive thermal diffusion layer for increased temperature rating and uniformity - Google Patents
Heater plate with embedded hyper-conductive thermal diffusion layer for increased temperature rating and uniformity Download PDFInfo
- Publication number
- US20110132896A1 US20110132896A1 US12/881,790 US88179010A US2011132896A1 US 20110132896 A1 US20110132896 A1 US 20110132896A1 US 88179010 A US88179010 A US 88179010A US 2011132896 A1 US2011132896 A1 US 2011132896A1
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- Prior art keywords
- heater
- diffuser
- plates
- metal plate
- diffusion layer
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B3/00—Ohmic-resistance heating
- H05B3/68—Heating arrangements specially adapted for cooking plates or analogous hot-plates
Definitions
- the present invention relates to heater plates and in particular to structural details of such heater plates specifically adapted to provide uniform heating.
- Achieving the most uniform temperature on the surface of a heater can be limited due to the thermal conductivity of the materials of construction. Often, material options are limited by factors such as temperature rating, chemical compatibility, or thermal expansion. Geometry of the heater can have a significant impact on asymmetric losses and aggravate thermal non-uniformity. Typically, experience and thermal modeling are used for the heater design for the most effective power distribution. Heat homogenizing ceramic materials may be used for the outer plates. Metallic heat spreaders, e.g., a copper core, may be used. But, even with the most effective heater layout and construction, the thermal uniformity may need still further improvement, as a typical heating plate at 250° C. may have a maximum-minimum range of as much as 15-20° C.
- TPG thermally annealed pyrolytic graphite
- the invention provides a uniform heater having a core formed of a thermally-annealed pyrolytic graphite (TPG) diffuser sandwiched between a first metal plate containing a heater element and a second metal plate providing a critical surface.
- the plates and TPG diffuser may be vacuum thermal brazed together.
- the TPG diffuser may have a molybdenum coating and nickel braze alloy sheets may be present between the diffuser and the respective plates.
- FIG. 1 is a top view of heater plate consistent with the present invention.
- FIG. 2 is a side exploded view of an embodiment of a heater plate of the present invention.
- FIG. 3 is a top view of a lower heater plate accommodating a heater coil.
- a heater 11 has a critical heating surface on a thermally conductive upper plate 13 .
- Two electrodes 19 and 21 for in internal heater coil are seen to emerge from a side of the heater 11 , along with a ground electrode 20 for the plate 13 .
- the heater 11 includes upper and lower plates 13 and 15 , together with and a thermal pyrolytic graphite (TPG) diffusion layer 17 and an electrically isolated heating element 23 located between the two plates 13 and 15 .
- TPG thermal pyrolytic graphite
- An interface material not shown, fills voids between the various component parts 13 , 15 , 17 and 21 , and bonds the plates 13 and 15 together.
- the upper and lower plates 13 and 15 may be made of metal.
- the plate material need not have especially high thermal conductivity in the plane of the plates because of the presence of the TPG diffusion layer 17 that serves to uniformly spread the heat from the heating element across the critical surface of the upper plate 13 .
- the plate material can be selected from a variety of metals, including stainless steels and nickel alloys, titanium, magnesium, molybdenum, tungsten, copper, aluminum, and combinations or alloys of the same.
- the stainless steels and nickel alloys are sold under a number of trade names, including AISI 304 and 316 stainless steels, Incoloy®, Iconel®, Hastelloy®, and Nickel 600 (UNS N06600). These metals and others can be used.
- the lower plate 15 may contain a spiral cavity to accept the heater element 23 .
- the cavity for the heater element 23 could be simply an open cavity with spaces between the coils of the heater element 23 filled with interface material.
- the upper plate may likewise contain a cavity to accept the TPG diffusion layer 17 .
- the TPG diffusion layer 17 may have a sputtered coating of molybdenum or other high-temperature sputter material that bonds to metal (where “high-temperature” refers to 500° C. or greater).
- Metals other than molybdenum that could be sputtered onto the TPG diffusion layer include nickel alloys, titanium, magnesium, tungsten, copper, aluminum, and combinations or alloys of the same.
- Interface material is any material added to fill voids between the two plates 13 and 15 and heater element 23 , such as a potting compound, as well as material to bond the two plates 13 and 15 , such as a braze material or cement.
- a braze material directly contacts the heater element 23 in the lower plate 15 to the coated TPG diffusion layer 17 in the upper plate 13 .
- a nickel braze clad such as Nickel 4777 (82Ni—7Cr—4Si—3Fe—3B) foil, may be provided between the coated TPG diffusion layer 17 and each of the plates 13 and 15 , and the entire assembly then vacuum furnace brazed.
- the results for the heater 11 of the present invention with TPG diffusion layer 17 were a maximum temperature of 244.88° C., a minimum temperature of 230.02° C., an average temperature of 240.50° C., and a standard deviation of 4.19° C.
- the results for the standard heater plate without the TPG diffusion layer were a maximum temperature of 260.01° C., a minimum temperature of 225.97° C., an average temperature of 249.87° C., and a standard deviation of 9.69° C.
- the temperature uniformity across the plate improved from ⁇ 17° C. for the standard plate to ⁇ 7° C. by adding the diffusion layer, a 59% reduction in AT.
Abstract
Description
- This application claims priority from U.S. provisional application Ser. No. 61/267,769, filed Dec. 8, 2009.
- The present invention relates to heater plates and in particular to structural details of such heater plates specifically adapted to provide uniform heating.
- Achieving the most uniform temperature on the surface of a heater can be limited due to the thermal conductivity of the materials of construction. Often, material options are limited by factors such as temperature rating, chemical compatibility, or thermal expansion. Geometry of the heater can have a significant impact on asymmetric losses and aggravate thermal non-uniformity. Typically, experience and thermal modeling are used for the heater design for the most effective power distribution. Heat homogenizing ceramic materials may be used for the outer plates. Metallic heat spreaders, e.g., a copper core, may be used. But, even with the most effective heater layout and construction, the thermal uniformity may need still further improvement, as a typical heating plate at 250° C. may have a maximum-minimum range of as much as 15-20° C. Examples of prior heaters are provided in U.S. Pat. Nos. 4,481,406 (Muka), 6,534,751 (Uchiyama et al.), 6,758,263 (Krassowski et al.) and U.S. Patent Application Publication No. 2009/0235866 (Kataigi et al.).
- Integrating a thermally annealed pyrolytic graphite (TPG) layer, between the heater and the critical surface of the plate dramatically improves the thermal uniformity. TPG is sometimes referred to as “hyper conductive” due to its having a thermal conductivity about four times that of copper. The high, in-plane thermal conductivity coefficient k allows for only shallow gradients. Thus, the provision of TPG material within a heater plate will help to distribute the heat from an isolated embedded heater element so that the operating surface of the plate has a more uniform temperature.
- In summary, the invention provides a uniform heater having a core formed of a thermally-annealed pyrolytic graphite (TPG) diffuser sandwiched between a first metal plate containing a heater element and a second metal plate providing a critical surface. The plates and TPG diffuser may be vacuum thermal brazed together. The TPG diffuser may have a molybdenum coating and nickel braze alloy sheets may be present between the diffuser and the respective plates.
-
FIG. 1 is a top view of heater plate consistent with the present invention. -
FIG. 2 is a side exploded view of an embodiment of a heater plate of the present invention. -
FIG. 3 is a top view of a lower heater plate accommodating a heater coil. - With reference to
FIG. 1 , aheater 11 has a critical heating surface on a thermally conductiveupper plate 13. Twoelectrodes heater 11, along with aground electrode 20 for theplate 13. - As seen in
FIG. 2 , theheater 11 includes upper andlower plates diffusion layer 17 and an electrically isolatedheating element 23 located between the twoplates various component parts plates - The upper and
lower plates TPG diffusion layer 17 that serves to uniformly spread the heat from the heating element across the critical surface of theupper plate 13. Thus, the plate material can be selected from a variety of metals, including stainless steels and nickel alloys, titanium, magnesium, molybdenum, tungsten, copper, aluminum, and combinations or alloys of the same. (The stainless steels and nickel alloys are sold under a number of trade names, including AISI 304 and 316 stainless steels, Incoloy®, Iconel®, Hastelloy®, and Nickel 600 (UNS N06600). These metals and others can be used.) - As seen in
FIG. 3 , thelower plate 15 may contain a spiral cavity to accept theheater element 23. Alternatively, the cavity for theheater element 23 could be simply an open cavity with spaces between the coils of theheater element 23 filled with interface material. The upper plate may likewise contain a cavity to accept theTPG diffusion layer 17. TheTPG diffusion layer 17 may have a sputtered coating of molybdenum or other high-temperature sputter material that bonds to metal (where “high-temperature” refers to 500° C. or greater). Metals other than molybdenum that could be sputtered onto the TPG diffusion layer include nickel alloys, titanium, magnesium, tungsten, copper, aluminum, and combinations or alloys of the same. - Interface material is any material added to fill voids between the two
plates heater element 23, such as a potting compound, as well as material to bond the twoplates heater element 23 in thelower plate 15 to the coatedTPG diffusion layer 17 in theupper plate 13. A nickel braze clad, such as Nickel 4777 (82Ni—7Cr—4Si—3Fe—3B) foil, may be provided between the coatedTPG diffusion layer 17 and each of theplates - For the heater element's electrical isolation (using MgO insulation), electrical resistance between the internal heater wire and its insulating sheath has a tendency to break down significantly starting around 450° C. To overcome this problem, we have increased the sheath diameter from a 0.125″ (3.2 mm) diameter element to a 0.188″ (4.8 mm) diameter element in order to increase the dielectric distance and are able to achieve 600° C. without bad leakage current. Additionally, higher temperature dielectrics, namely boron nitride, could replace the MgO as the heater element's insulating sheath. The isolation material, while providing electrical resistance, should also have good thermal conductivity. Boron nitride has this combination of properties.
- To determine the effect of the hyper-
conductive diffusion layer 17 inheater plate 11, we used an existing design for thelower plate 15 andheater element 23, and made anupper plate 13 with the addeddiffusion layer 17 of TPG. Bothheater plates diffusion layer 17 was fused into a cavity between theheater element 23 and theupper plate 15. The critical surfaces on the outside of the upper plate for both the embodiment of the present invention so made and a standard heater plate of the prior art without theTPG heater layer 17 were painted with a high temperature flat black paint to insure consistent emissivity for infrared evaluation. Both plates were placed in a chamber on small ceramic standoffs for side-by-side thermal imaging. Thermal images were taken in both atmosphere and vacuum. IR analysis settings were 21° C. ambient, 0.95 emissivity, lens factor 1, 16″ focus, 6×4.5 cm field of view, high temperature range of 265.82° C., and low temperature range of 26.69° C. for a test at nominal heater temperature 250° C. The results for theheater 11 of the present invention withTPG diffusion layer 17 were a maximum temperature of 244.88° C., a minimum temperature of 230.02° C., an average temperature of 240.50° C., and a standard deviation of 4.19° C. The results for the standard heater plate without the TPG diffusion layer were a maximum temperature of 260.01° C., a minimum temperature of 225.97° C., an average temperature of 249.87° C., and a standard deviation of 9.69° C. The temperature uniformity across the plate improved from ±17° C. for the standard plate to ±7° C. by adding the diffusion layer, a 59% reduction in AT.
Claims (15)
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US26776909P | 2009-12-08 | 2009-12-08 | |
US12/881,790 US8481896B2 (en) | 2009-12-08 | 2010-09-14 | Heater plate with embedded hyper-conductive thermal diffusion layer for increased temperature rating and uniformity |
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Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
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USRE46136E1 (en) * | 2006-09-19 | 2016-09-06 | Momentive Performance Materials | Heating apparatus with enhanced thermal uniformity and method for making thereof |
Citations (11)
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US4481406A (en) * | 1983-01-21 | 1984-11-06 | Varian Associates, Inc. | Heater assembly for thermal processing of a semiconductor wafer in a vacuum chamber |
US4742324A (en) * | 1984-04-27 | 1988-05-03 | Sumitomo Metal Industries Ltd. | Sheath heater |
US5343022A (en) * | 1992-09-29 | 1994-08-30 | Advanced Ceramics Corporation | Pyrolytic boron nitride heating unit |
US5348215A (en) * | 1992-11-04 | 1994-09-20 | Kevin Rafferty | Method of bonding hard metal objects |
WO1996009738A1 (en) * | 1994-09-20 | 1996-03-28 | Negawatt Gmbh | Electric heating element |
US5863467A (en) * | 1996-05-03 | 1999-01-26 | Advanced Ceramics Corporation | High thermal conductivity composite and method |
US6147334A (en) * | 1998-06-30 | 2000-11-14 | Marchi Associates, Inc. | Laminated paddle heater and brazing process |
US6534751B2 (en) * | 2000-02-28 | 2003-03-18 | Kyocera Corporation | Wafer heating apparatus and ceramic heater, and method for producing the same |
US6758263B2 (en) * | 2001-12-13 | 2004-07-06 | Advanced Energy Technology Inc. | Heat dissipating component using high conducting inserts |
US20090235866A1 (en) * | 2008-03-21 | 2009-09-24 | Ngk Insulators, Ltd. | Ceramic heater |
US7901509B2 (en) * | 2006-09-19 | 2011-03-08 | Momentive Performance Materials Inc. | Heating apparatus with enhanced thermal uniformity and method for making thereof |
-
2010
- 2010-09-14 US US12/881,790 patent/US8481896B2/en active Active
Patent Citations (11)
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US4481406A (en) * | 1983-01-21 | 1984-11-06 | Varian Associates, Inc. | Heater assembly for thermal processing of a semiconductor wafer in a vacuum chamber |
US4742324A (en) * | 1984-04-27 | 1988-05-03 | Sumitomo Metal Industries Ltd. | Sheath heater |
US5343022A (en) * | 1992-09-29 | 1994-08-30 | Advanced Ceramics Corporation | Pyrolytic boron nitride heating unit |
US5348215A (en) * | 1992-11-04 | 1994-09-20 | Kevin Rafferty | Method of bonding hard metal objects |
WO1996009738A1 (en) * | 1994-09-20 | 1996-03-28 | Negawatt Gmbh | Electric heating element |
US5863467A (en) * | 1996-05-03 | 1999-01-26 | Advanced Ceramics Corporation | High thermal conductivity composite and method |
US6147334A (en) * | 1998-06-30 | 2000-11-14 | Marchi Associates, Inc. | Laminated paddle heater and brazing process |
US6534751B2 (en) * | 2000-02-28 | 2003-03-18 | Kyocera Corporation | Wafer heating apparatus and ceramic heater, and method for producing the same |
US6758263B2 (en) * | 2001-12-13 | 2004-07-06 | Advanced Energy Technology Inc. | Heat dissipating component using high conducting inserts |
US7901509B2 (en) * | 2006-09-19 | 2011-03-08 | Momentive Performance Materials Inc. | Heating apparatus with enhanced thermal uniformity and method for making thereof |
US20090235866A1 (en) * | 2008-03-21 | 2009-09-24 | Ngk Insulators, Ltd. | Ceramic heater |
Non-Patent Citations (1)
Title |
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Accuratus Corporation, Boron Nitride, BN Material Properties, 2002. * |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
USRE46136E1 (en) * | 2006-09-19 | 2016-09-06 | Momentive Performance Materials | Heating apparatus with enhanced thermal uniformity and method for making thereof |
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